Implantable cardiac devices typically sense cardiac electrical signals in an implantee and classify the implantee's cardiac rhythm as normal/benign or malignant. Illustrative malignant rhythms may include ventricular fibrillation and/or polymorphic ventricular tachyarrhythmia. The accuracy with which an implantable medical device analyzes sensed signals determines how well it makes therapy determinations and other decisions.
New and/or alternative methods and devices for cardiac signal analysis are desired.